Adaptive delta codec which varies a delta signal in accordance with a characteristic of an input analog signal

Claim 1

An adaptive delta codec comprising: delta coding means which compares the level of an analog input signal and an estimated signal, and generates a coded signal in response to the result of the comparison; first and second control terminals which receive control signals indicative of the increase or decrease in a delta signal and the estimated signal; first and second storing means for respectively storing the delta signal and the estimated signal; adder/subtractor means connected to said first and second storing means in time-division manner, and which decreases an absolute value of the estimated signal in the second storing means during a first time period, changes the delta signal in said first storing means in accordance with the level at said first control terminal during a second time period, and makes an addition or subtraction of the delta signal and the estimated signal in accordance with the level at said second control terminal during a third period, the result of the addition or subtraction in the third period being stored in the second storing means as a new estimated signal.